This application is a divisional of copending application Ser. No. 09/911,811, filed Jul. 24, 2001.
1. Field of the Invention
The present invention is directed to an arrangement for data follow-up for a warmup cycle of an ink jet print head. The invention is utilized in ink jet printer devices, for example in a postage meter machine with an ink jet print head, a printing station of a mail processing machine or other printer devices.
2. Description of the Prior Art
German Patentschrift 196 05 015 (U.S. Pat. No. 5,949,444) discloses a printer device of the JetMail® postage meter machine in detail. With a non-horizontal, approximately vertical letter transport, a franking imprint is implemented with an ink jet print head stationarily arranged in a recess behind a guide plate. A trigger sensor for the printing process is arranged shortly before the recess for the ink jet print head, which recognizes the start of the letter and interacts with an incremental sensor for path control. The printing process is triggered by a transmitted light barrier of the JetMail® postage meter machine (European Patent 901 108). The leading edge even of pieces of mail that are especially thick is thus unambiguously recognized. Further optical sensors for recognizing a mail jam and for path control are also utilized in the JetMail® device. In addition to these sensors, at least one sensor for sensing a print block of the print head is utilized, such as a heating resistor, this being likewise connected to the postage meter machine control via an internal interface circuit of the postage meter machine. An internal postage meter machine interface circuit is disclosed in European Patent 716 398 (U.S. Pat. No. 5,710,721). For example, the print block contains three ink printing modules. In conformity with an embodiment disclosed in European Application 713 776 (U.S. Pat. No. 5,757,402), the ink printing modules are arranged between identically constructed circuit modules, the latter respectively carrying a heating resistor and a sensor. In order also to assure a high printing quality of the JetMail® postage meter machine even given a low ambient temperature, the print block, and thus the ink as well, are preheated to a predetermined temperature. Printing is only allowed within a specific temperature range, since the temperature of the ink has a considerable influence on the droplet formation during the ink ejection. When the ambient temperature lies at a temperature Terror=0° C. below the minimum operating temperature Tmin=32° C. of the JetMail®, damage to the print head can occur due to excessively large temperature differences during heat-up. The printing quality becomes poorer above the maximum operating temperature Tmax=50° C. of the JetMail® system. In both instances, at least one error message is generated. There are thus competing considerations between assuring a high print quality and achieving an immediate readiness of the printer device.
Other ink jet printers or postage meter machines with ink jet printer technology, for example with bubble jet technology, also must reach a predetermined operating temperature before the print block or the printer is enabled for printing. A sensor constantly measures the temperature in the ink print head. The specific warmup data are redetermined for each ink cartridge every time the device is turned on. A repeated spray-rinsing is thereby cyclically implemented and a large ink volume is thus wasted. For the purpose of an ink spraying, it is necessary to electrically heat a heating resistor arranged close to a nozzle such that some of the water of the aqueous ink suddenly evaporates (bubble jet principle). The ink jet print head is driven with print voltage pulses of approximately 12 V and a duration of approximately 1.9-2.3 μs. A drop if ink is thereby accelerated to the surface of a print medium or, if no print medium is present, to the opening of an ink sump container. The local heating also leads to the gradual rise of the temperature in the broader environment of the heating resistor. A printing pause, in contrast, leads to the gradual drop of the temperature. In particular, an ink jet printer connected to a personal computer that is restarted daily requires too long a preparation time for the printing job. Given ½-inch ink jet cartridges, for example, 22 temperature values of the print head that belong to a respective print pulse voltage value are measured after turn-on. Each nozzle is driven one thousand times per measurement with the print pulse voltage value that has been set. In the next measurement, the nozzle is driven a thousand times with a print pulse voltage value that is set lower. The course of the temperature curve measured in this way is interpreted. The print pulse voltage value that is derived is employed for the subsequent printing. The ambient temperature likewise has an influence in the measurement. The preparation time that is thus required then has a predetermined duration of approximately 1 minute.
If, on the other hand, a start could be undertaken proceeding from a standby mode for the ink jet printer, then this could allow an immediate implementation of the print job. The correct operating temperature 15-40° C. is retained when the ink jet print head is operated in the standby mode without printing a print medium. The operating temperature can be maintained during printing given a shorter printing pause or in the standby mode by electrically heating the heating resistor close to each nozzle such that hardly any or no water of the aqueous ink evaporates. An energy pulse of approximately 0.75 μm then suffices only for the warmup (pulse warming-up) but not yet for printing. For achieving a longer service life of the cartridge, the PWU method (pulse warming-up) also is employed after the turn-on. Given an ambient temperature range of 10-40° C., too, a warmup time must elapse if an operating temperature of approximately 45° C. is to be achieved again. A longer time must pass below the indicated range of the ambient temperature. A predetermined operating temperature also can be maintained with a stronger energy pulse that is supplied in time intervals wherein printing is not performed. Although this allows an immediate printing, a stronger energy pulse >2 μs leads to ink spraying. The ink supply of a cartridge, however, is limited to approximately 42 ml and thus also is consumed in the standby mode. Since the ink cartridges hold a far lower ink volume than, for example, the ink tank of the JetMail® postage meter machine, the service life of the ink cartridge would be considerably shortened by each and every additional ink consumption during warmup.
U.S. Pat. No. 5,625,384 discloses an ink jet printer with replaceable ink print heads, whereby the characteristic data of each specific head are determined during the production of the cartridge and stored in the ROM on the head, i.e. before an initial placement in the ink jet printer. The head operating conditions thus can be automatically called. The replacement of a head is automatically recognized on the basis of identification information. An ink jet head that is re-introduced (re-used), however, cannot be operated with the optimum conditions if too long a time interval has passed before the re-introduction. When the re-introduced ink print head has only a residual ink supply available to it, however, a restoration of conditions that guarantee a long service life of the ink print head could be foregone. However, there is no possibility of shortening the time span after the re-introduction until the renewed operation of the head farther, and the latter is always operated with the same data stored during production.